Method and system for synchronising loads before injection on a tilt tray type sorting system

ABSTRACT

A method for synchronizing loads before the injection thereof on a sorting machine, consisting of trays which pass in front of an injection system comprising conveyors for moving the loads towards an injection site, a synchronization conveyor for positioning a load in order to place it on a tray, a device for injecting a load from the synchronization conveyor onto the machine and a cell for detecting the position of the loads at the exit of the synchronization conveyor. When a load passes the cell, the synchronization conveyor and the injection device are reversed and accelerated slightly to a top speed of V AR , SO that the load returns to obscure the cell; the reverse movement is maintained until the cell is no longer obscured; and the synchronization conveyor is moved forward and accelerated slightly to a top speed of V AV  until the cell is obscured.

[0001] The present invention relates to a method for synchronizing loadsbefore injection onto a sorting system, in particular a tilt tray typesorting machine. It also relates to a system for the implementation ofthis method.

[0002] These machines are made up of a chain of carts moving around atrack, generally in a loop, but which can also be in the form of a railcircuit with semi-autonomous carts using DCV technology, at apredetermined non-zero speed. Each cart is equipped with a tilt tray,which allows for the load being carried to be discharged at apredetermined location, according to known processes.

[0003] The invention relates to the injection method, that is, theprocess allowing for a pre-determined tray to be loaded with a load suchas a parcel or a piece of baggage.

[0004] Particularly with regard to baggage, the loads have a widevariety of geometrical shapes, materials and various appendages (straps,belts, retractable wheels, etc.) and are of variable masses, which makestheir grip, and consequently their kinematic behaviour, practicallyunpredictable.

[0005] The invention describes a method for improving the reliability ofinjection, that is, the correct positioning of each load takenindividually on a sorting machine tray.

[0006]FIG. 1 schematically describes how an injection devicerepresentative of the state of the art is constructed, the behaviour ofan unstable load according to the known injection methods and the meansof detecting this abnormal behaviour.

[0007]FIG. 1A describes the construction of a normal start/stop typeinjection line, using motorized conveyors.

[0008]FIG. 1B illustrates the normal positioning of a load beforeinjection onto a sorting machine.

[0009]FIG. 1C illustrates the abnormal positioning of a sliding orrolling load on an injection line.

[0010]FIG. 1D illustrates the position of an injection line in asecurity check circuit for a baggage handling system.

[0011] The arrows indicate the direction of movement of the loads.

[0012]FIG. 1A shows a top view of a set of trays 1AP moving at apre-determined speed in front of the injection device, which is made upof the following, in the order of movement of the loads:

[0013] two spacer type conveyors 1AQ1, 1AQ2 well known in the art, whichensure the movement of the loads one by one towards the actual injectiondevice,

[0014] a synchronization conveyor 1AS, the function of which is to placethe load in a position allowing for it to be placed on a tray inballistic mode,

[0015] an injection device 1AI, generally made up of a set of drivebelts, which carries out such placement.

[0016] The loads are individually presented to the conveyor 1ASaccording to known processes, which consist of positioning them one byone so that their front edge obscures the photoelectric cells 1AQ1C,1AQ2C.

[0017] As soon as the conveyor 1AS is emptied of the previous load, theconveyor is started according to a pre-determined acceleration law y1until the cell 1AS1 is obscured, and then according to a pre-determinedacceleration law γ2 until the cell 1AS2 is obscured.

[0018] At this stage, the controls simultaneously start the conveyor 1ASand the injection device 1AI to give the load a speed, the component inthe direction of travel of the trays on the sorting machine of which isequal to the linear speed of the said trays.

[0019] As a point of information, injection at 45° relative to thesorting machine means that this injection speed is of the order of{square root}2× the linear speed of the sorting machine. The means ofstabilizing the load despite the transverse component are known. Thisonly occurs when the motorized conveyors are driving the load withoutany notable sliding or rolling, as shown in FIG. 1B.

[0020] When the load does not have the required grip or is likely toroll on the conveyors, the situation is as shown in FIG. 1C, where theload has overshot the obscuring position for the cell 1AS2.

[0021] In the known state of the art, this situation, which means thatthe correct placing of the load on a tray on the sorting machine cannotbe foreseen, can be detected.

[0022] In the known state of the art, the automatic controls trigger analarm (for example a stop and a light signal) to request humanintervention.

[0023] There are injection lines in the known state of the art known asdynamic injection lines, designed in such a way that they only stop theloads if the sorting machine does not have sufficient empty trays toallow for the load to continue moving.

[0024] However, if this is not the case, this type of injection line,which largely reproduces the risk related to the load sliding or rollingas already described, also has a stand-by stop.

[0025] The management of such incidents presents a certain number ofknown disadvantages, particularly when the injection line is part of abaggage handling and sorting system.

[0026] One of the requirements of such systems is the systematicinspection of the baggage for the detection of any suspicious contentssuch as explosives.

[0027] Such detection takes place through the insertion of a specialistapparatus and intermediate conveyor means upstream of the injection linefor final sorting, as illustrated in the diagram in FIG. 1D.

[0028] This apparatus includes:

[0029] baggage identification means (1D1), for example the opticalreading of a bar code printed on a label when the baggage was checkedin,

[0030] means of detecting the possible presence of suspicious contents(1D2), such as X-ray apparatus.

[0031] After identification, the intermediate conveyor devices and theinjection must use known methods to reliably monitor the position of thebaggage, in order to keep track of the identification and status,suspicious or not, of each checked piece of baggage.

[0032] For example, it is customary to use a sorting machine to sendboth risk-free baggage to its final destination (aircraft loadingstation) and baggage that presents a risk to stations for closerinspection.

[0033] The slippage of a piece of baggage on injection therefore createsa situation of uncertainty with regard to the location of one or evenseveral pieces of baggage.

[0034] In the known injection techniques, the detection of a slippagerequires human intervention that consists of:

[0035] either removing the piece of baggage for manual handling,

[0036] or repositioning it so that it obscures the cell 1AS2 again,which, as long as the control means permit, allows for the normalprocess to continue with the loss of monitoring considered to becorrected.

[0037] In any case, the said human intervention results in:

[0038] operating costs linked to the availability of sufficientcompetent operators,

[0039] risks linked to human error with regard to security.

[0040] For example, some baggage sorting installations are manned tothis end by as many operators as injections, thus considerably adding tooperating expenses.

[0041] In any case, each injection stoppage results in a loss ofthroughput that prejudices the operational output of the system.

[0042] The aim of the present invention is to remedy these disadvantagesby proposing an injection procedure that in most cases allows for thepositioning of the loads to be automatically corrected before injection,so that human intervention and the related costs are significantlyreduced.

[0043] This aim is achieved with a method for synchronizing loads beforetheir injection onto a tilt tray type sorting machine, this machinehaving a set of trays moving at a pre-determined speed in front of aninjection system made up of conveyor means to move the loads one by onetowards an injection site, a so-called synchronization conveyor 1AS toplace a load coming from the said conveyor means in a position allowingfor it to be placed on a tray in ballistic mode, a device 1AI to injecta load coming from the said synchronization conveyor onto the sortingmachine, and means of detecting the position of the loads within theinjection system comprising a detection cell arranged approximately atthe exit of the synchronization conveyor.

[0044] According to the invention, when a load has overshot the exitdetection cell, the following stages take place:

[0045] control of the synchronization conveyor 1AS and the injectiondevice 1AI according to a reversal with slight acceleration and a topspeed of a pre-determined value V_(AR), so that the load returns toobscure the exit detection cell 1AS2,

[0046] continuation of the reversal control until the exit detectioncell 1AS2 is no longer obscured, and then for a pre-determined period,and

[0047] control of the synchronization conveyor according to a movementforwards with slight acceleration and a top speed of a predeterminedvalue V_(AV) until the exit detection cell 1AS2 is obscured.

[0048] This method also increases the security of the baggage handlingsystems by correcting the reliable monitoring of the said baggage.

[0049] An important characteristic of the method is that it does notusually require any additional material resources during theelectromechanical design of the injection lines.

[0050] Moreover, it is applicable to injections already in service inexisting installations, which consequently allows for a clear reductionin the operating costs of such installations.

[0051] The invention applies equally to known start/stop typeinjections, where each load pauses for synchronization with the sortingmachine, or dynamic injections, where this pause only occurs if thetrays that could be aimed for according to a continuous process areoccupied.

[0052] The synchronization method according to the invention generallycomprises the following stages:

[0053] movement forwards control of the said conveyors and thesynchronization conveyor according to a first pre-determined controllaw, until a second detection cell is obscured,

[0054] movement forwards control of the synchronization conveyoraccording to a second pre-determined control law, until the exitdetection cell is obscured,

[0055] at the end of a pre-determined dwell time, test of the exitdetection cell.

[0056] This method is therefore characterized by the following stages:

[0057] if the test indicates that the said exit detection cell is stillobscured, operation of the injection device,

[0058] if the said exit detection cell is not obscured, reversal controlof the synchronization conveyor and the injection device according to athird pre-determined control law, until the exit detection cell isobscured,

[0059] continued reversal control of the synchronization conveyoraccording to a fourth pre-determined control law until the exitdetection cell is no longer obscured,

[0060] stopping control of the synchronization conveyor 1AS for apre-determined period, and

[0061] movement forwards control of the synchronization conveyoraccording to a fifth pre-determined control law, until the exitdetection cell is obscured.

[0062] The successive stages of the control of the synchronizationconveyor and the injection device according to either the first, second,third, fourth or fifth control law are advantageously repeated until theexit detection cell test shows that the said exit detection cell isstill obscured after a pre-determined dwell time.

[0063] The synchronization method according to the invention is, forexample, implemented by programming a synchronization control unit, inconnection with the control of drive motors for the synchronizationconveyor and the injection device, the said synchronization control unitbeing equipped to receive signals sent by the exit cells.

[0064] It can thus be implemented on a specific synchronization controlunit added to a pre-existing injection command/control equipment.

[0065] In this configuration, the control signals for thesynchronization conveyor and injection device drive motors generated bythe pre-existing control equipment are reproduced exactly at theterminals of the specific control unit, and the specific control unit isprovided with a loss of synchronization alarm signal generated by thepre-existing command/control equipment.

[0066] According to another aspect of the invention, a system isproposed to synchronize loads before their injection onto a tilt traytype sorting machine, for the implementation of the synchronizationmethod according to any one of the previous claims, characterized inthat it comprises:

[0067] first means to control the synchronization conveyor and theinjection device, when a load has overshot the exit detection cell,according to a reversal with slight acceleration and a top speed of apre-determined value V_(AR), so that the load returns to obscure theexit detection cell,

[0068] these first control means being designed to be activated untilthe exit detection cell is no longer obscured, and for a predeterminedperiod, and

[0069] second means to control the conveyor according to a forwardmovement with slight acceleration and a top speed of a pre-determinedvalue V_(AV) until the exit detection cell is obscured.

[0070] The synchronization system according to the invention can beembodied in the form of a specific control unit dedicated tosynchronization, transparent to a pre-existing injection command/controlunit. It may also comprise an additional detection cell to replace orsupplement a pre-existing exit detection cell.

[0071] The synchronization system according to the invention may beimplemented on a dynamic injection site comprising at least onesynchronization conveyor with a load stop position and a synchronizationsensor.

[0072] The description below gives other specific features andadvantages of the invention. On the attached drawings, given asnon-limitative examples,

[0073]FIG. 2A shows, in a first embodiment of a synchronization systemaccording to the invention, a reversal sequence of the synchronizationconveyor and the injection device;

[0074]FIG. 2B shows, in this first embodiment, the continuation of thereversal sequence,

[0075]FIG. 2C shows, in this first embodiment, a subsequent forwardmovement sequence of the synchronization conveyor and the injectiondevice, and

[0076]FIG. 3 shows a second embodiment of a synchronization systemaccording to the invention.

[0077] For the implementation of the synchronization method according tothe invention, the drive motors of the synchronization conveyor 1AS andinjection device 1AI must have two directions of movement. The controlfor these motors must in practice be a speed variator, allowing forpre-determined control of the acceleration and drive speed.

[0078] When a load has overshot the exit detection cell 1AS2, thefollowing stages take place within the context of the synchronizationmethod according to the invention:

[0079] communicating to the synchronization conveyor 1AS and theinjection device 1AI a reversal (FIG. 2A) with slight acceleration and atop speed of a predetermined value V_(AR), so that the load returns toobscure the cell 1AS2 normally,

[0080] continuating this movement until the cell 1AS2 is no longerobscured (FIG. 2B) and then continuation for a pre-determined period: atthis point, the injection device 1AI motor is restored to its normalmovement direction and setting,

[0081] communicating to the conveyor a forward movement (FIG. 2C) withslight acceleration and a top speed of a predetermined value V_(AV)until the cell 1AS2 is obscured.

[0082] The aim of the synchronization method according to the inventiondescribed above is thus to return the load to the normally plannedposition before the actual injection movement.

[0083] The speed setting values are chosen so that most loads that areunstable at a normal speed can be driven without sliding or rolling.

[0084] Because the synchronization method is automatic and the only loadexisting on the perimeter of the conveyors 1AS and 1AI can only be thatpreviously introduced from the spacer conveyor 1AQ2, the completeaccomplishment of the manoeuvre restores the monitoring of the load,i.e. the link between the identity of the load and its position isre-established.

[0085] The complete synchronization process, with correction to restorethe positioning and monitoring of the load in the event that it slidesor rolls, is broken down into stages, the first four of which are knownin the prior art, namely:

[0086] 1) according to a first pre-determined law, the conveyor 1AQ2 andthe synchronization conveyor 1AS are controlled in forward movementuntil the cell 1AS1 is obscured,

[0087] 2) according to a second pre-determined law, the conveyor 1AS iscontrolled in forward movement until the cell 1AS2 is obscured,

[0088] 3) a predetermined dwell time is observed,

[0089] 4) the cell 1AS2 is tested again,

[0090] 5) if the cell is still obscured, the actual injection movementis triggered, synchronized with the passing of an empty tray; if it isnot, an alarm is triggered to request human intervention.

[0091] Of course, each of stages (1) to (3) is accompanied by a dwelltime limit for the detection of other faults outside the scope of theinvention.

[0092] The synchronization method according to the invention consists inparticular of replacing stage (5) by stage (6) and the following stages:

[0093] 6) if the cell is still obscured, the actual injection movementis triggered; if it is not, according to a third predetermined law theconveyors 1AI and 1AS are controlled in reverse until the cell 1AS2 isobscured,

[0094] 7) according to a fourth pre-determined law, the conveyor 1AScontinues in reverse until the cell 1AS2 is no longer obscured,

[0095] 8) conveyor 1AS is stopped, and a predetermined dwell time isobserved (optionally zero),

[0096] 9) according to a fifth pre-determined law, the conveyor 1AS iscontrolled in a forward movement until the cell 1AS2 is obscured,

[0097] 10) stages (3) to (5) are carried out.

[0098] Each of the movement stages (6) to (9) is accompanied by a dwelltime limit for the detection of other faults outside the scope of theinvention.

[0099] Technically, the synchronization method according to theinvention may be embodied by the programming of a control unit such asan industrial controller of any known type, in connection with thecontrol of the motors for the conveyors 1AS and 1AI and the cells 1AS1and 1AS2.

[0100] According to a first embodiment of the invention, the method isadvantageously integrated into the injection from the design stage.

[0101] According to a second embodiment described in FIG. 3, thesynchronization method according to the invention is managed by aspecific piece of equipment that is added to a preexisting injection.This second embodiment is advantageously applicable to a sortinginstallation that is already in regular service, with no need to altereither the mechanics or the pre-existing command/control equipment.

[0102] The operation to implement the invention consists of:

[0103] replacing or modifying speed variators of the existingsynchronization conveyor 3S and of the existing injection device 3I toobtain two directions of movement and a range of speed settings allowingfor the method to be implemented.

[0104] exactly reproducing the control signals SC of the motors that areknown by the pre-existing command/control equipment, at the terminals ofthe specific control unit 3C,

[0105] connecting the “loss of synchronization” alarm signal 3Pgenerated by the pre-existing command/control equipment to the unit 3C,

[0106] optionally, installing an additional cell 3S3 if the position ofthe pre-existing cell 3S2 is not suitable, and connecting either 3S3 or3S2 in parallel to the unit 3C,

[0107] connecting an output from the specific control unit 3C to thereset input 3R of the existing command/control equipment,

[0108] if necessary, connecting the specific control unit 3C to theinstallation monitoring computer, via a data transmission link 3T.

[0109] In normal operation, the specific control unit 3C, which may bean industrial controller, is completely neutral and “transparent” to theexisting command/control equipment.

[0110] When the existing command/control equipment emits the alarmsignal 3P, it is known in advance that this command/control equipmenthas suspended all movement, waiting for an intervention.

[0111] From this moment, the specific control unit 3C takes control ofthe conveyors 3S and 3I, to carry out the method according to stages (6)to (9) described above, using the preexisting cell 3S2 or the auxiliarycell 3S3 as a guide.

[0112] If the manoeuvre fails (due to the expiry of the guard timers),the specific control unit 3C simply gives control of the motors to thepreexisting command/control equipment.

[0113] If the manoeuvre succeeds, the specific control unit 3C resetsthe existing command/control equipment and then gives it control of themotors.

[0114] Any installation of this type is designed to return to normaloperation after an interruption such as a power failure. Therefore, whenit has been reset, the existing command/control equipment returns to anormal situation and will complete the injection.

[0115] Generally, the existing command/control equipment will have senta fault message to the monitoring computer. The data link 3T is providedto this end, to send this same computer a specific fault cancellationmessage.

[0116] Of course, the invention is not limited to the examples describedabove and numerous adjustments can be made to these examples withoutleaving the scope of the invention.

[0117] A person skilled in the art will easily understand that theinvention naturally extends to dynamic injections, where there is atleast one synchronization conveyor with a load stop position and aspecific sensor analogous to the cells 1AS2 or 3S2 described above. Aperson skilled in the art will also understand that it is easy, simplyby using relays, to create specific control units that are totallytransparent to existing command/control equipment to control the motors.In this case, the power to the specific unit must simply be cut off toreturn fully to the prior operation. This last point is important forintervention on systems In regular service, on which only a few hoursper day (for example, the closure of an airport at night) are generallyavailable to carry out the modification.

[0118] Thus, the synchronization method according to the invention mayequally be implemented on new systems and on systems in service, andprovides in all cases a significant reduction in the injection failurerate and consequently a rapid return on investment and/or improvedperformance of the sorting machines.

[0119] It is also important to note that in terms of airport security,the clear reduction in losses of monitoring and human interventionprovides additional quality in the so called hold baggage control chain.

1. Method for synchronizing loads before their injection onto a tilt tray type sorting machine, this machine comprising a set of trays (1AP) moving at a pre-determined speed in front of an injection system comprising conveyor means (1AQ1, 1AQ2) to advance the loads one by one towards an injection site, a so called synchronization conveyor (1AS) to position a load coming from the said conveyor means in a position allowing for it to be placed on a tray in ballistic mode, a device (1AI) for injecting a load coming from the said synchronization conveyor onto the sorting machine, and means of detecting the position of the loads within the injection system comprising a detection cell (1AS2) arranged approximately at the exit of the synchronization conveyor (1AS), characterized in that when a load has overshot the exit detection cell (1AS2), the following stages take place: control of the synchronization conveyor (1AS) and the injection device 1AI according to a reverse movement with slight acceleration and a top speed of a pre-determined value V_(AR), so that the load returns to obscure the exit detection cell (1AS2). continuation of the reversal control until the exit detection cell (1AS2) is no longer obscured, and then for a pre-determined period, and control of the synchronization conveyor according to a forward movement with slight acceleration and a top speed of a predetermined value V_(AV) until the exit detection cell (1AS2) is obscured.
 2. Method according to claim 1, comprising the following stages: control of the said conveyor means and the synchronization conveyor (1AS) in a forward movement according to a first predetermined control law, until a second detection cell (1AS1) is obscured, control of the synchronization conveyor (1AS) in a forward movement according to a second predetermined control law, until the exit detection cell (1AS2) is obscured, at the end of a pre-determined dwell time, testing of the exit detection cell (1AS2), characterized by the following stages: if this test shows that the said exit detection cell (1AS2) is still obscured, operation of the injection device (1AI), if the said exit detection cell (1AS2) is not obscured, control of the synchronization conveyor (1AS) and the injection device (1AI) in reverse mode according to a third pre-determined control law, until the exit detection cell (1AS2) is obscured, continuation of the reverse control of the synchronization conveyor (1AS) according to a fourth pre-determined control law, until the exit detection cell (1AS2) is no longer obscured, stop control of the synchronization conveyor (1AS) for a pre-determined period, and control of the synchronization conveyor (1AS) in forward mode according to a fifth predetermined control law, until the exit detection cell is obscured.
 3. Synchronisation method according to claim 2, characterized in that the successive control stages of the synchronization conveyor and the injection device according successively to the first, second, third, fourth and fifth control laws are repeated until the exit detection cell test shows that the said exit detection cell is still obscured at the end of a predetermined dwell time.
 4. Method according to any one of the preceding claims, characterized in that it is implemented by programming a synchronization control unit, in connection with the control of the synchronization conveyor (1AS) and the injection device (1AI) drive motors, the said synchronization control unit being equipped to receive signals sent by the exit detection cells (1AS1) and (1AS2).
 5. Method according to any one of the preceding claims, characterized in that it is implemented in a specific synchronization control unit added to pre-existing injection command/control equipment.
 6. Method according to claim 5, characterized by the following stages, the control signals (SC) for the drive motors for the synchronization conveyor and injection device generated by the pre-existing command/control equipment are reproduced exactly at the terminals of the specific control unit (3C), and the specific control unit (3C) is provided with a loss of synchronization alarm signal (3P) generated by the preexisting command and control equipment.
 7. System for synchronizing loads before their injection onto a tilt tray type sorting machine, for the implementation of the synchronization method according to any one of the preceding claims, characterized in that it comprises: first means to control the synchronization conveyor (1AS) and the injection device (1AI), when a load has overshot the cell (1AS2), in a reverse movement with slight acceleration and a top speed of a predetermined value V_(AR), so that the load returns to obscure the cell (1AS2), these first control means being designed to be activated until the cell (1AS2) is no longer obscured, and for a pre-determined period, and second means to control the conveyor in a forward movement with slight acceleration and to a top speed of a predetermined value V_(AV) until the cell is obscured (1AS2).
 8. System according to claim 7, characterized in that it is embodied in the form of a specific control unit dedicated to synchronization, transparent to a pre-existing injection command/control unit.
 9. System according to claim 8, characterized in that it also comprises an additional detection cell (3S3) to replace or supplement a preexisting exit detection cell (3S2).
 10. System according to one of claims 8 or 9, characterized in that the specific control unit (3C) is connected to a monitoring computer for the sorting installation, via a data link (3T), in particular to transmit a fault message and a fault cancellation message.
 11. System according to any one of claims 7 to 10, characterized in that it is implemented on a dynamic injection site comprising at least one synchronization conveyor with a load stop position and a synchronization sensor.
 12. Application of the synchronization method according to any one of claims 1 to 6 to a new baggage sorting system.
 13. Application of the synchronization method according to any one of claims 1 to 6 to an existing baggage sorting system. 